Phase balancer



Aug. 25, 1925.

R. D. EVANS PHASE BALANCER Filed se t. 28, 1923.

WITNESSES: 2

INVENTOR Rober T D E vans.

M ATTORNEY Patented 25, 1925.

UNITED STATES OFFICE.

nozennr n. EVANS, or ILKINSB BG, rnnnsYI vAnia, ASSIGNOR 'ro lwEsrIneHoU sE ELECTRIC & MANUFACTURING CQMBANY, A QQBI'QBATION 0F rENNsYLvANIA,

enl st Balances.

Application filed. September a, 1923. 'se rial iib, sagas.

Z all whom it may] concern Be it known that I, RoisnnrD. EVANS, a citizen of the United States, and a resident of lVilkinsburg, in thefcounty of Allegheny and State of Pennsylvania, have invented a new and useful Improven'ient in PhaseBalancers, of which the following is specication. l e r My invention relates to polyphase electrical systems, and has particular reference to the problem of balancing either the currents or the voltages thereof. n

An object ofmy invention is to derive, from a polyphase line, a system of polyphase voltages: which may be varied in phase amlinagnitude and which may have either the positive or the negative phasesequeiice. A more specific object of my invention is to provide a ook phase induction regulator and, a group of singlephase induction regulators tor cont-rolling the phase and the m Q'nitude, respectively,of the booster electromotive force in order to produce balanced voltage or current conditions in an unbalanced polyphase line. I

A; further object of my invention is to provide automatic regulating apparatus for balancing a. polyphase line, as outlined a bore.

Wit-h these and other objects in view, my

inventirm consists in the combinations and arrangements described in the following specification and illustrated in the accompanying drawing, wherein Z I Figure 1. is a diagrammatic View of cireuits and apparatus embodying my invention as applied to the problem of securing balanced voltages in a-n'unbalanced; line, and Fig, 2.is a similar view illustrating my invention as applied to the problem of obtaining balanced currents from an'unbalanced polyphase line. 4 I V In the system shown in Fig. 1, a long transmission line 3 is shown supplying an unbalanced load 4,- and a polyphase feeder line requiring balanced voltages. Energy is supplied to the distant endof the transmission line from any suitable source lo]- cated at 6. By reason of the unbalanced currents drawn by the load device 4:, the unbalanced line drops inthelongtransmission line will cause unbalanced voltage conditions to exist at the point of connection of the feeder line 5 on which it is] desired to maintain balanced voltages I provide,

lator 7 of polyphase voltages, having" a variable magnitude and constant phase relationship, and a polyphase induct-ionregulator for securing a var ation 1n the phase of the booster voltage without varying its magnitude,"

Qiiepf the voltage regulating devices is c'ormected in pjarallel, t0. the line, while the other is com ected, in series with the line and is energized from the parallel-connected regulating device.

1 Intlie form shown Fig. 1, a polyphase ii iduction regulator 7, is provided ha-vinga polyphase primary, winding 8 anda polyphase secondary winding 9, the respective phases of the secondary winding being connected in series with the respective phase conductors of the line. The primary windings '8 are energized, in reverse phase-sequence, from the secondary windings of a bank of single-phase induction regulators 1Q, 11 and 12 having their primary windings energized from the transmission line on the balanced or load side of the polyphase regu- In order to control the booster vo-1tage, ,I provide any suitable indicating device, shown as ,a, static network.1 3 having the property of producing a volt-age which is proportional, in phase and in magnitude, to the negative phase sequence, component of the line voltages ,on the unbalanced side ram polyphase, induction regulator. .The static network lficomprises a circuit. comprising a resistance. 34,:- for drawing a current in phase withone oft-he phases ,of the line Voltage, and a second circuit compris- 111g a resistancefifiand an inductance 36 hayinga total, ii'npedance..equa1 to. the resistance 3% andf s'o propontionedas to draw a current lagging behind another or the phases of the line voltage. The currents',, in the two. circuits are passed through an. equalizer, coil or, auto} transformer "3 7 The, phase connections are such that,.,f or balanced positive-phase; sequence line vo1tages,, the currents v the two halves, of the equalizer coil 37 are equal and displaced, in the lagging direction, l20 +6O:18O from one another, and no voltage appears across the equalizer coil as a result of such balanced positive-phasesequence line voltages. For negative-phasesequence line voltages, the phase that was lagging will be leading, and the equalizer coil currents will be displaced, in the leading direction, 120-60:60. There will thus be a voltage across the equalizer coil proportional to the phase and the magnitude of the negativephase-sequence line volta e.

The static network .per se constitutes the subject-matter of the specification and claims oi my copending application Serial No. 3478,4 10, filed Feb. 13, 1920.

A dill'erential relay l l is provided for balancing the voltage of the network 13 against the voltage of the secondary winding of one of the sii'igle-phase induction regulators, as 12, whereby a. small regulat ing motor 15 energized in the one or the other direction, as may be necessary to maintain the booster voltage equal in mag- ,iitude to the negative-phasesequence component of the unbalanced line voltages. The regulating motor 15 is connected to adjust the three single-phase induction regulators in unison, through any suitable mechanical coupling, indicated at 16.

The relative angular positions of the primary and secondary members of the polyphase induction regulator 7 are controlled means of a small-regulating motor 17 which is energized in the one 01' the other direction by means of a phase-responsive relay 18, which may be of any suitable or well-known type for indicating the departure, in either direction, of the phase 01 the booster voltage "from the condition of exact phase opposition with respect to the phase oi the negativephase-sequence component of the line voltage.

In operation, the single-phase induction regulators draw such currents from the polyphase line as to generate the necessary negativephase-sequence booster voltages in the secondary windings 9 of the polyphase induction regulator. Thus, the line voltages are balanced while the currents supplied by the source 6 remain unbalanced.

In Fig. 2 is shown a system for maintaining a balanced current flow notwithstanding the fact that the voltages on one or both sides of the balancing apparatus may be unbalanced. I have indicated a polyphase line 19 carrying currents which are unbalanced at the right-hand terminals 20 of the line, as by reasion of an unbalanced furnace load 4a In order to produce balanced current conditions at the leithand terminals 21 of the line, I provide shunt-connected appara tus for dr. ving unbalanced currents of such 1 agnitude and phase relation as" to neutral- 'ze the negative-phasesequence components of the unbalanced currents flowing in the line at the right-hand terminals 20.

Any suitable negative-phase-sequence current-indicating device, shown as astatic network 22, is employed for deriving currents or voltages which are proportional, in phase and magnitude, to the negative-phase-scquenee component of the line currents, at the right-hand end of the line. The static network 22 is similar, in principle, to the voltage-responsive network 13. It comprises two current transformers 3S and 39 which are responsive to two phases of the line current and are closed-circuited, respectively, by the resistance 10 and the resistance and inductance aggregate 41. The instrument terminals of the network are connected to be responsive to the vectorial sum of the voltage drops in the impcdances 4:0 and 41, whereby a resultant voltage is produced only in response to the negativephase-sequence line currents.

A plurality of single-phase inductance regulators 23, 2s and are connected, in this instance, in series with the line and having their secondary windings connected in star to energize the primary windings 26 015 a. polyphase induction regulator 27. The settings of the three single-phase regulators are independently controlled by means of three small regulating motors 23a, 24a and 25a, respectively, which are energized, in the one or the other direction, in accordance with the movements of three diii'erential relays 436, 2-1?) and 25?), which balance the current from the network 22 against the current in the corresponding phase of the primary windings 26, as indicated.

The polyphase induction regulator 27 is provided with secondary windings 28 which are connected, in reverse phase-sequence, across the left-hand end oi the polyphase line 19, in order to draw negative-phasc-sequence currents which are equal to the negatire-phase-sequeuce current components flowing in the right hand end of the line and which are opposite in phase thereto.

A second network 220, for measuring the negative-phase-sequence current components, is associated with the terminal conductors ot the secondary winding 28 and is utilized to energize the polyphase primary windings 29 of a power-factor meter 30, said meter being shown as having a singlephase secondary winding 31 energized in ac cordance with the currents flowing in the first-mentioned network 22. The powerfactor meter is provided with a pair of contact devices 32, whereby a small regulating motor 33 is energized, in the one or the other direction, to regulate the relative phase positions of the primary and sec ondary windings of the polyphase induction regulator 27, as may be necessary to maintain the phase of the negative-phasesequence currents drawn by the secondary windings 28 exactly in phase-opposition to the negative-phase-sequence components 01 the line currents flowing in the right-hand terminals of the line 19. In this manner, the currents in the line 19 are balanced, while the voltages will, in general, be unbalanced on at least one end of the line.

While I have illustrated and described two different modifications of n y invent-ion,

it will be obvious that many modifications may be made by those skilled in the art without departing from the spirit of my invention, and that, in all cases, thepower may belflowing in either direction. hen, for convenience of expression, I speak of power as flowing in a certain direction, I mean to include also the case of reverse energy-flow. I desire, therefore, that the language of the accompanying claims shall be construed in the light of, the foregoing statements in so far as may be consistent with the disclosures of the prior art.

I claim as my invention: l XThe combination with a polyphase line,

of means for deriving power from said line and generating substantially symmetrical poly-phase power of the same frequency as the line, having an electrical quantity of variable voltage ratio but having a'constant phase relation, and a second means for interchanging power of the same frequency, having an electrical quantity of variable phase but constant voltage ratio, between said first-mentioned means and said line, one of said means being connected in series with the line and the other being connected in shunt thereto.

2. The combination with a polyphase line having a phases, of means comprising n single-phase induction regulators associated therewith, and means comprising a polyphase induction regulator interchanging power between said single-phase regulators and said line, one of said means being connected in series with the line and the other bein connected in shunt thereto.

The combination with an unbalanced polyphase line, of means for deriving power from said line and generating substantially symmetrical polyphase power of the same frequency as the line, having an electrical quantity of variable voltage ratio but constant phase relation, and a second means for interchanging negative-phase-sequence power of the same frequency, having an electrical quantity of variable phase but constant voltage ratio, between said firstmentioned means and said line, one of said means being connected in series with the line and the other being connected in shunt thereto.

i. The combination with an unbalanced power, havim polyphase line having it phases, of means comprising a single-phase induction regulators associated therewith, and means comprising a polyphase induction regulator interchangmg power between said s1ngle p'liase regulators and said llne, one of said 'means being connected in series with the line and the other being connected in shunt thereto, the phase sequences of said means be- Ting reversed, the one with respect to the and generating substantially symmetrical polyphase power having an electrical quantity of variable voltage ratio but having a constant phase relation, a, second means for interchanging powerhaving an electrical quantity of variable phase but constant voltage ratio, between said first-mentioned 'means and said line, one of said means hein ,9; connected in series with the line and the other being connected in shunt thereto, electro-responsive means for automatically controllingsaid first and said second-mentioned means, respectively, in accordance with the magnitude and phase of a quantity in said line. 7 i

V 6. The combination with a polyphase line having a phases, of means comprising'n single-phase induction regulators associated therewith, means comprising a polyphase induction regulator interchanging power between said single-phase regulators and said line, one of said means being connected in series with the line and the other being connected in shunt thereto, electroresponsive means for automatically controlling said first and said second-mentioned means, respectively, in accordance with the magni tude and phase of an electrical quantity in said line.

7. The combination with an unbalanced polyphase line, of means for deriving power from said line and generating substantially symmetrical polyphase power having an electrical quantity of variable voltage ratio but constant phase relation, a second means for interchanging negative-phase-sequence g an electrical quantity of variable phase but constant voltage ratio, between said first-mentioned means and said line, one of said means being connected in series with the line and the other being connected in shunt thereto, and electro-responsive means for automatically controlling said first and said second-mentioned means, respectively, in accordance with the magni tude and phase of a negativephase-sequence quantity in said line whereby saidquantity may be neutralized.

8. The combination with an unbalanced polyphase line having n phases, of means comprising at single-phase induction regulators associated therewith, and means comprising a polyphase induction regulator intel-changing power between said single-phase regulators and said line, one of said means being connected in series with the line and the other being connected in shunt thereto, and electroresponsive means for automatically controlling said first and said second mentioned means, 1' spective y, in accord anee with the magnitude and )hase of a negative-phase-sequence quantity in said line whereby said quantity may be neutralized.

The combination with a three-phase line, of a three-phase induction regulator having primary windings and secondary windings, said secondary windings being connected in. series with said line, and three single-phase induction regulators having their primary windings connected in parallel. to the respective phases of said line and having their secondary windings connected to the primary windings of said three-phase regulator.

10. The combination with a three-pliase line, of a three-phase induction regulator having primary windings and secondary windings, said secondary windings being connected in series with said line, electroresponsive means for maintaining the phas of the secondary eleetroinotive forces of said three-phase regulator substantially opposite to the phase of a line-voltage component, three single-phase induction regulators having their primary windings connected in parallel to the respective phases of said line and having their secondary windings con nected to the primary windings of said three-phase regulator, and electro-responsive means for simultaneously regulating all of said single-phase regulators in accordance with the magnitude of electrical conditions in the line.

11. The combination with a threesphaz'se line having unbalanced voltages, of a threephase induction regulator having primary windings and secondary windings, said secondary windings being connected in series with said line for substantially balancing the voltage thereof, and three singlophase induction regulators having their primary windings connected in parallel to the T091360- tive phases of? said line on the balanced side of said three-phase regulator and having their secondary windings connected in reverse phase sequence, to the primary windings of saiu three-phase regulator.

12. The combination with a three-phase line having imbalanced voltages, of a threephase induction regulator having primary windings and secondary windings, said secondar -J windings being connected in series with said line for substantially balancing the voltage thereof, electroa-esponsive means for maintaininn' the phase of the secondary elec tromotive iorces at said three-phase regulator substantially opposite to the corresponding phase of the corresponding negativephase-seqnence line-voltage component, three single phase induction regulators having their primary windings connected in paralle to the respective phases oi" said line on the balanced side of said three-phase regulator and having their secondary windings (v nected, in reverse phase-sequence, to tire E mary windings of said. threei, )l'1as-:e regu ator, and electro-responsive means for siinultaneonsly regulating all of said singlephase regulators in accordance with the magnitude of the corresponding negative-phase-s qnence electrical conditions in the line.

In testimony whereof, I have hereunto subscribed my name this 22nd day of September 1928. i

R0 BERT I). E V All S. 

